High Energy Physics - Theory

Title:On some aspects of the definition of scattering states in quantum field theory

Abstract: The problem of extending quantum-mechanical formal scattering theory to a
more general class of models that also includes quantum field theories is
discussed, with the aim of clarifying certain aspects of the definition of
scattering states. As the strong limit is not suitable for the definition of
scattering states in quantum field theory, some other limiting procedure is
needed. Two possibilities are considered, the abelian limit and adiabatic
switching. Formulas for the scattering states based on both methods are
discussed, and it is found that generally there are significant differences
between the two approaches. As an illustration of the application and the
features of these formulas, S-matrix elements and energy corrections in two
quantum field theoretical models are calculated using (generalized)
old-fashioned perturbation theory. The two methods are found to give equivalent
results.